It is well known in the art of ink jet printing to attach replaceable containers of ink and solvent to ink systems of ink jet printers in order that fluid in the ink system can be topped up as required. Inks and solvents used in ink jet printing are frequently volatile and noxious, and it is therefore desirable to provide clean and safe ways by which they may be handled. It is also very important that the correct ink or solvent is used for a given application, and that this ink or solvent is not contaminated in any way. It is therefore an object of the invention to allow replacement ink and solvent containers to be attached and removed cleanly and simply, without spillage, to and from an ink jet printer, and it is also desirable to ensure that the ink and solvent are attached correctly to the ink jet printer.
It has previously been proposed to provide the containers with screw-threaded connections and also to fit the containers with snap-on rotatable rings having protrusions spaced appropriately to mate with recesses in cooperating member to which the container is intended for attachment, see WO-A-93/1890. Whilst such connections systems may operate satisfactorily, because the rings are snap fitted to the containers and provide the sole mechanism for preventing incorrect fitting (the containers otherwise being the same, it is possible for the wrong rings to be fitted and for the system to fail to prevent the wrong connections being made. Screw-threaded connections are also slow to operate.